效果图

function fn ()
{
var dl = +new Date();
console.log(dl);
var str = '';
for (var i = 0; i < 1000; i++)
{
document.body.innerHTML += '<div style="width:100px;height:2px;border:1px solid blue;"></div>'
}
var d2 = +new Date();
console.log(d2 - dl);
}
fn()